In the art of thermal ink jet printing, it is known to use flexible (flex) circuits to provide driving current to a plurality of heater resistors which are photolithographically defined on a thin film resistor (TFR) type thermal ink jet printhead. This flex circuit connection is sometimes accomplished by providing dimples at preselected areas in the flex circuit and using these dimples to mate with corresponding electrical contact areas on the thermal ink jet printhead. Pressure pads are applied on the reverse side of the flex circuit and in the concave reverse surfaces of the dimples to provide the necessary compressive forces to make good electrical contact between the thermal ink jet printhead and the flex circuit. Thus, good firm and continuous electrical connections are maintained between the flex circuit and the thermal ink jet printhead as the printhead moves rapidly back and forth along a platen during a thermal ink jet printing operation.
During this latter motion, a loop in the flex circuit rolls back and forth along the length of the platen at a relatively high speed and with frequent jerking and direction reversal motions. Accordingly, it is imperative that this good firm electrical connection between the flex circuit and the printhead be continuously maintained once the thermal ink jet printhead and associated ink reservoir housing are locked into position in the printhead carriage. This type of printhead and flex circuit connection is disclosed, for example, in the Hewlett-Packard Journal, Volume 36, Number 5, May 1985, incorporated herein by reference.
Whereas the above approach to making flex circuit contacts to thermal ink jet printheads has proven generally satisfactory in many respects, the above requirement for applying pressure pads to the dimples in the flex circuit necessitates providing a corresponding space for these dimples and pads. A part of this space requirement is defined by a vertical space dimension in the Z direction with respect to the XY plane of the printhead, and such vertical dimension represents a significant percentage of the total vertical space available within the printhead carriage. Futhermore, the lateral dimension of the dimples and the corresponding space requirement therefor in the horizontal or XY plane of the printhead imposes a corresponding limitation on how much the printhead surface area can be reduced.